linux-kernel - Re: [patch -rt 2/2] KVM: lapic: mark LAPIC timer handler as irqsafe

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Date:	Thu, 4 Dec 2014 11:43:52 -0200
From:	Marcelo Tosatti <mtosatti@...hat.com>
To:	Paolo Bonzini <pbonzini@...hat.com>
Cc:	linux-kernel@...r.kernel.org,
	Luiz Capitulino <lcapitulino@...hat.com>,
	Rik van Riel <riel@...hat.com>,
	Steven Rostedt <srostedt@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>, kvm@...r.kernel.org
Subject: Re: [patch -rt 2/2] KVM: lapic: mark LAPIC timer handler as irqsafe

On Tue, Nov 25, 2014 at 06:38:04PM +0100, Paolo Bonzini wrote:
> 
> 
> On 25/11/2014 18:21, Marcelo Tosatti wrote:
> > +
> > +	if (r == HRTIMER_RESTART) {
> > +		do {
> > +			ret = hrtimer_start_expires(data, HRTIMER_MODE_ABS);
> > +			if (ret == -ETIME)
> > +				hrtimer_add_expires_ns(&ktimer->timer,
> > +							ktimer->period);
> 
> Is it possible to just compute the time where the next interrupt
> happens?  

Yes but there is no guarantee hrtimer_start_expires will not fail.

> I suspect the printk and WARN_ON below can be easily triggered
> by a guest.

I'll remove those, thanks.


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